Polyvinyl chloride resin composition having excellent transparency and impact strength

ABSTRACT

PVC resin compositions of improved transparency and impact are obtained by mixing the PVC with a graft polymer. The graft is produced by grafting first styrene and then methyl methacrylate onto an elastomer of butadiene, n-butyl acrylate, and styrene in the proportions shown in the accompanying ternary constitutional diagram. When the monomer(s) used in preparing the aforesaid graft polymer have a small quantity of C10 to C18 saturated fatty acid dissolved therein, the PVC compositions prepared from the graft polymer show further improvements in their properties.

United States Patent- STRENGTH Inventors: Fumio Ide; Kenji Okano; SeijiDeguchi, all

of Hiroshima, Japan Assignees: Mitsubishi Rayon Co., Ltd.; NittoChemical Industry Co., Ltd., Tokyo, Japan Filed: July 9, 1969 Appl. No.:840,240

Foreign Application Priority Data July 10, 1968 Japan ..43/48360 July12, 1968 Japan ..43/48854 US. Cl ..260/23.7 R, 260/23 XA, 260/23.7 M,

260/876 R Int. Cl. ..C08f 29/22 Field of Search ..260/876, 23.7, 23 X,890, 80.7

Ide et al. 51 Feb. 22, 1972 [54] POLYVINYL CHLORIDE RESIN 1 R f r ncCited COMPOSITION HAVING EXCELLENT UNITED STATES PATENTS TRANSPARENCYAND IMPACT 3,288,886 11/1966 Himei et al. ..260/876 3,312,756 4/1967Baer et a1 ..260/876 Primary Examiner-Donald E. Czaja AssistantExaminerDonalcl J. Barrack Attorney-William D. Hall, Elliott I. Pollock,Fred C. Philpitt, George Vande Sande, Charles F. Steininger and RobertR. Priddy [57] ABSTRACT PVC resin compositions ofimproved transparencyand impact are obtained by mixing the PVC with a graft polymer. Thegraft is produced by grafting first styrene and then methyl methacrylateonto an elastomer of butadiene, n-butyl acrylate, and styrene in theproportions shown in the accompanying ternary constitutional diagram.When the monomer(s) used in preparing the aforesaid graft polymer have asmall quantity of C to C saturated fatty acid dissolved therein, the PVCcompositions prepared from the graft polymer show further improvementsin their properties.

4 Claims, 1 Drawing Figure POLYVINYL CHLORIDE RESIN COMPOSITION HAVINGEXCELLENT TRANSPARENCY AND IMPACT STRENGTH The present invention relatesto a resin composition mainly comprising a polyvinyl chloride resin(hereinafter called PVC resin") and having excellent transparency andhigh impact strength, in particular, to a resin composition comprising97-60 parts by weight of a PVC resin and 3-40 parts by weight of a graftpolymer prepared by polymerizing first styrene in the presence of anelastomer obtained by copolymerizing 75-30 percent by weight1,3-butadiene, 5-30 percent by weight n-butyl acrylate, and 20-50percent by weight styrene and thereafter polymerizing methylmethacrylate.

Furthermore, when in the case of polymerizing the monomers in thepresence of the elastomer, a higher saturated fatty acid is added to atleast one of the monomers, the graft polymer obtained greatly enhancesthe processabilty and the impact strength of the PVC resin composition.

PVC resins are generally inexpensive and have excellent chemical andphysical properties. Thus, they are produced commercially on a largescale for many widely varying uses. However, such resins are somewhatinferior in impact strength and hence various studies have been made forovercoming such a difficulty and various improvements have beenreported,

It has been suggested that the impact resistance of PVC resins could beimproved by blending them with natural or synthetic rubber, or athermoplastic resin having such rubber as the base. Although thusobtained modified PVC resin composition shows an improved impactstrength as compared with that of the original PVC resin, thecomposition is generally inferior severely in transparency, that is, thetransparency which is one of the merits of PVC resin is severely reducedby improving the impact strength.

it has also been reported that when PVC resin is blended with a resinprepared by graft polymerizing a monomer such as styrene, methylmethacrylate, acrylonitrile, etc., to an elastomer such as polybutadieneor styrene-butadiene copolymer (hereinafter called SBR"), a compositionhaving an improved impact resistance could be obtained without fatallyreducing the transparency of PVC resin.

However, the resin composition having excellent transparency can beprepared by only strictly controlled conditions. When polybutadiene isemployed as elastomer for the composition, it is required that theparticle size thereof be as small as possible, the gel content (theproportion of such parts that are insoluble in organic solvent such astuluene) be high, and the swelling index thereof be low. Also, when SBRis used as the elastomer, the particle size thereof is also required tobe small. Furthermore, in any case of employing polybutadiene and SBR.the combination thereof with the kind of monomer grafted to theelastomer must be strictly selected. The reasons why such strictrestrictions are necessary in the case of employing polybutadiene or SBRas the elastomer are that the refractive index thereof is different fromthat of PVC resin and also the elastomer has poor compatibility with PVCresin.

An object of the present invention is to improve the low impact strengthof PVC resin without reducing the transparency thereof.

Other object of this invention is to provide a resin composition havingexcellent transparency, high impact resistance even if a PVC resinhaving a relatively low polymerization degree.

Further object of this invention is to provide a resin compositionhaving excellent transparency and high impact resistance even by using amolding machine having a weak mixing power.

As the results of various investigations for obtaining the compositionwithout having aforesaid faults, the inventors have found an elastomerdifferent from conventional elastomers provides a resin compositionhaving excellent properties and by using such elastomer and selectingthe combination of the monomer to be graft polymerized to the elastomerand the polymerization conditions, an excellent resin composition havingimproved impact strength together with excellent transparency can beobtained.

The portion within area ABCD in the ternary constitutional diagram ofthe accompanying drawing shows the range of the initial monomercomposition constituting the elastomer of l,3-butadiene, n-butylacrylate, and styrene used for preparing the resin composition of thepresent invention. Straight line I in the figure stands for theazeotropic composition in which the initial monomer composition of1,3-butadiene, nbutyl acrylate, and styrene is same as the compositionthereof in the polymer formed at any moment of polymerization and theazeotropic composition gives the most excellent transparency to theterpolymer itself. Straight line m stands for the composition providingan index of refraction like that of polyvinyl chloride.

By only using the elastomers having such compositions as above, the hightransparency can be provided to copolymer prepared therefrom. However ifone of such a monomer as other acrylic esters than n-butyl acrylate,vinyl chloride, vinylidene chloride, or acrylonitrile instead of n-butylacrylate in the elastomer are used, the elastomer thus prepared cannotgive a resin composition having excellent transparency and high impactresistance.

The merit of using the aforesaid elastomer in the present invention isthat the control of the particle size of the elastomer particles is notso important as in the case of using polybutadiene or SBR. For example,in the case of using polybutadiene or SBR, a good transparency cannot beprovided to a PVC resin composition if the elastomer particles havingparticle sizes less than 0.2 micron are not present therein in aproportion of higher than percent. On the other hand, in the case ofusing the aforesaid elastomer of this invention, a good transparency canbe provided to a resin composition even if the elastomer particleshaving the particle sizes of higher than 0.2 micron are present in aproportion of only about 40 percent by weight.

Moreover, when SBR is employed as the elastomer, the resin has unevenstructure and also the transparency and other properties of the finalproduct are largely influenced by the conversion of polymerization ofSBR since the structure and the refractive index thereof are varied bythe variation in conversion of polymerization thereof. On the otherhand, as the elastomer used in the present invention has an azeotropiccomposition or a composition similar to the azeotropic composition, theelastomer is scarcely influenced by the conversion of polymerization andhas a very homogeneous structure.

The composition of the present invention comprises a graft polymer (I)prepared by grafting styrene to a 1,3-butadiene-nbutyl acrylate-styreneelastomer (hereinafter, called elastomer (E)) and then grafting methylmethacrylate and PVC resin (II).

Graft polymer (I) which is one component of the resin composition of thepresent invention may be prepared by grafting first styrene to elastomer(E) while adding the monomer to a latex of the elastomer in one fellswoop or continuously and then grafting methyl methacrylate theretowhile adding the latter monomer in one fell swoop of continuously(process A) but in order to particularly facilitate the kneading of thegraft polymer with PVC resin, the graft polymerization is conducted bydissolving a saturated fatty acid having 10-18 carbon atoms in at leastone of styrene and methyl methacrylate to be grafted in an amount of0.5-5 parts by weight per parts by weight of the graft polymer andadding continuously the solutionto the polymerization system (processB).

The resin composition consisting of the graft polymer prepared by any ofthe aforesaid processes and a PVC resin is quite excellent in impactstrength as compared with a resin composition of a graft polymerprepared by grafting a mixture of styrene and methyl methacrylatesimultaneously to the elastomer and a PVC resin, and further even if theaverage polymerization degree of the PVC resin employed for producingthe resin composition is low, the impact strength of the compositionthus prepared is very high. Moreover, when the graft polymer prepared byusing the monomers shown above, at least one of which contains asaturated fatty acid having -18 carbon atoms employed, the resincomposition prepared from the graft polymer and a PVC resin is veryeffective for providing a product having'excellent impact strength byusing a molding machine having a weak kneading power.

The typical examples of the saturated fatty acid used in process B shownabove are capric acid, palmitic acid, lauric acid, myristic acid, andstearic acid and they may be used individually or as a mixture thereof.

in the case of conducting the graft polymerization by process A, styreneand/or methyl methacrylate may be added in one fell swoop orcontinuously.

When the monomer is added continuously, the sheet or film formed byextruding the resin composition is superior in smoothness slightly tothe case of adding the monomer in one fell swoop and also the board ofthe composition formed by molding is superior in transparency butslightly lower in impact strength.

On the other hand, in process B wherein the saturated fatty acid isemployed, it is necessary to add continuously the monomer containing thesaturated fatty acid to the elastomer (E) over at least a 30-minuteperiod and otherwise, a large amount of coagulates are formed, whichreduce the transparency of the final product.

Furthermore, it is necessary that graft polymer (I) be composed of 30-70percent by weight elastomer (E) and 70-30 percent by weight of the totalamount of styrene and methyl methacrylate to be grafted thereto, andalso the graft monomer to be grafted be composed of l0-50 percent byweight of methyl methacrylate and 90-50 percent by weight of styrene. Ifa graft polymer having other composition than above is employed, atleast one of the transparency, impact resistance and other mechanicalproperties of the resin composition prepared therefrom will be reduced.

The graft polymerization is generally carried out at a temperature of30-l 00 C., in the presence ofa usual polymerization initiator,Furthermore, if necessary, a small amount of an emulsifier, a chaintransfer agent and a modifier may be employed.

The latex of the graft polymer thus prepared is coagulated by a knownmethod, washed with water and then dried.

PVC resin (ll) which is another component of the resin composition ofthe present invention may be polyvinyl chloride or a copolymer of morethan 70 percent by weight of vinyl chloride and less than 30 percent byweight of at least one monomer of vinyl bromide, vinylidene chloride,vinyl acetate, acrylic acid and methacrylic acid. The PVC resin used inthe present invention may be prepared by a conventional emulsionpolymerization, suspension polymerization, or bulk polymerization.

For obtaining the resin composition of this invention, 3-40 parts byweight of graft polymer (l) is blended with 97-60 parts by weight of PVCresin (II) to provide 100 parts by weight of the final product. When theproportion of graft polymer (1) is less than 3 parts by weight, noeffect of adding the polymer is obtained, while if the proportion of thepolymer is higher than 40 parts by weight, other excellent properties ofPVC resin than transparency will be lowered as well as the use of such alarge proportion of polymer is not economical. The particularlypreferable composition of the present invention comprises l0-30 parts byweight of graft polymer (l) and 90-70 parts by weight of PVC resin (ll).

Graft polymer (l) is blended with PVC resin (1]) by using a conventionalmixing means. For example, they may be mixed by a mixing roll, a Banburymixer, or a plastograph as well as a molding machine such as acompounding extruder and a blow molder. Also, they may be premixed bymeans of a ribbon blender or a Henschel mixer before mixing them bymeans of the aforesaid mixing machine. Moreover, as mixing, there may beadded to the system, if necessary, a conventional stabilizer, aplasticizer, a lubricating agent, a pigment, a filler, etc.

The invention is illustrated in part by the following examples, whichare given for the purpose of showing several ways in which the inventionmay be practiced and not for the purpose of limiting the invention. inthe examples, part" and percent mean part by weight" and percent byweight" respectively.

EXAMPLES 1-3 Preparation of Elastomcr (E-l) l.3-Butadiene 57 partsn-Butyl acrylate l0 parts Styrene I 33 parts Potassium oleate )2 2 puttsPotassium persulfate )2 0.3 parts t-Dodecyl mcrcaptun )2 0.5 partsDeionized Water I parts The above mixture was charged to an autoclaveand after purging with nitrogen, the charge was polymerized for 15 hoursat 55 C. with stirring to provide the elastomer (E-l) in a conversion of97 percent based on the monomers charged. Preparation ofGraft Polymer(G-l) Elustomer 13-1 50 parts (by solid content) Styrene 30 parts Methylmethacrylute 20 parts Potassium persulfate (total) 0.5 parts Deionizedwater 200 parts Thus, according to the aforesaid composition, 30 partsof styrene and 0.3 part of potassium persulfate were first added to alatex of elastomer (E-l and the mixture was reacted for 3 hours at 70 C.in nitrogen atmosphere. Thereafter, 20 parts of methyl methacrylate andremaining 0.2 part of potassium persulfate were added to the productthus prepared and then the graft polymerization was carried out for 3hours at 70 C. to provide a latex of graft polymer (G-l The latex ofgraft polymer thus formed was coagulated by a 0.2 percent aqueoussulfuric acid solution followed by washing with water and then drying toprovide white powders ofgraft polymer (G-l ln a Henschel mixer wereblended the graft polymer and PVC resin (having average degree ofpolymerization P of 750) together with 2 parts of di-butyl-tin-maleate,1 part of butyl stearate and 1 part of dibutyl-tin-laurate per 100 partsof PVC resin for 20 minutes. The compound thus obtained was extruded bymeans of an extruder having T-die at l C. to provide a sheet of theresin composition and the properties of the sheet were measured, theresults of which are shown in Table l.

in addition, two specimens having other compositions than thecomposition of this invention were prepared for comparison and theresults of measuring the properties of them are also shown in the tableas comparative examples.

1 Measured according to 13815244955 (0.3 mm sheet thick).

2 Total luminous transmittance measured according to ASTM D 1003-61(press molded sheet).

8 Measured according to ASTM D1003-61.

4 Undestroyed.

EXAMPLE 4-9 The elastomers having the compositions shown in Table 2 wereprepared and graft polymers were prepared using the elastomers. The sameprocedure as in Example 1 was conducted using the graft polymers and PVC(P 750) to provide parts of methyl methacrylate was grafted thereto toprovide the resin composition of the present invention and thepropergraft polymers. Resin compositions consisting of i5 parts of tiesof them were measured. For comparison, other resin comthe graft polymersand 85 parts of PVC (P 730) were prepared positions than those of thepresent invention having the comand their luminous transmittances weremeasured. the results position outside the area ABCD of the ternaryconstitutional 5 of which are shown in Table 3.

diagram were prepared and the propertie of them were also Forcomparison, comparative resin compositions prepared measured. by usingthe same amount of polybutadiene or SBR (23.5 per- Each graft polymerwas prepared by grafting first 27 parts of n sty ene) r p ep ed n h ir lminous transstyrene in the presence of a latex containing 55 parts ofmitlflnees r l m sured. elastomer having an average particle size of0.15 micron and 10 As clear from Table 3, the transpal'tmcy of the rh bf i 13 parts f rh l methacrylate, position prepared by usingpolybutadiene or SBR as elastomer TABLE 2 Elastomer Total compositionImpact luminous (percent) Position strength transmitin the PVC/graft(kg.-cin./ tance Bd BA St diagram polymer mm.) (percent) Example 4 57 1033 a 90:10 80.6 80.2 57 10 33 a 85:15 126. 5 80. 1 45 12 43 13 90-1078.4 78 4 45 12 43 b 85 15 120.1 78 2 40 40 C 90.10 76.3 77 8 9 40 20 40c 85:15 118.9 77 0 Comp ative exa 3 75 0 (1 90:10 81.2 71 0 75 0 25 (185-15 127.4 63 8 100 0 0 e 90 10 82.3 60 7 100 0 0 e 85.1 127.4 51 6 5228 20 f 85:15 67.6 63 3 8.. 17 33 50 g 85:15 48.3 54 0N0'rE.Bd=1,3-butadiene; BA=nbuty1 acrylate; St=styrene.

As is clear f rom Table 2, the use of elastomers having comwas largelyinfluenced by the particle size of the elastomer. positions defined bypoints included in the area ABCD in That is, in the case of usingpolybutadiene, the transparency of figure results in resin compositionshaving excellent trans-v the resin composition was reduced when theparticle size of parency as compared to those prepared with theelastomer the elastomer was larger than 0.12 micron and also in the casehavmg Composmons Outslde the area ABCD- of using SBR as the elastomer,the transparency was reduced when the article size was lar er than 0.18micron. On the EXAMPLES 10-13 g other hand, in the case of using theelastomer 111 the present 1n- Elastomer latices each having differentaverage particle vention, the resin composition having good transparencywas sizes were prepared by using a mixture of57 percent 1,3-buobtainedeven when the elastomer having a comparatively tadiene. 10 percentn-butyl acrylate, and 33 percent styrene. large particle size wasemployed.

TABLE 4 Properties of the products Grafting monomer Luminouscompositions trans- Gr'aiting Impact mittance Haze St MMA methodstrength (percent) (percent),

MMA=Methy1 methacrylate. St=Styrene. I=2-stage grafting method (St. wasfirst polymerized in the presence of elastomer and then MMA waspolymerized).

II=1-stage grafting method (a mixture of MMA and St was polymerized inthe presence of elastomer). v H TABLE 3 This is because the elastomerused in the present invention Averagepap Totanumi 0 has a uniformcomponent distribution, and a good compatii l Size of H0118 trensbihtywith and a nearly same refractive index as those of PVC theelastomermittance Elastomer employed 0, (percent) and also provide a graftpolymer having a high grafting efficiency since the elastomer isproperly swollen with the Example.

10 Bd[BA/St=57/10/33 0,03 5 monomer to be grafted to the elastomer.ssweltering;-

t 18 77. 4 1a Bd/BA/St=57/10/33 0.22 75.1 EXAMPLES 1446 ComparativeExample:

n Polybutadiene 0.08 68,6 To 50 parts of the elastomer consisting of 57percent 1,3- 15 "I138: 3: g 2%; butadiene, 10 percent n-butyl acrylateand 33 percent styrene n ion 8.3g was grafted 50 parts of the monomersas shown in Table 4 to "1 SB 1" provide graft polymers. The propertiesof the resin composig- 35% 8-32 ggg tion consisting of 8 parts of thegraft polymers and 92 parts of PVC having a degree of polymerization of710 are shown in Table 4. I

As shown in the above table, the comparative specimens 75 Thereafter 30parts f styrene was fir t grafted i the were inferior in luminoustransmittance and impact strength presence of a latex of 50 parts of theelastomer and then 20 and also when methyl methacrylate and styrene weregrafted simultaneously, the resin composition prepared had no excellentproperties.

EXAMPLE 17 To 40 parts of the elastomer consisting of 53 percent 1,3-butadiene, percent n-butyl acrylate, and 32 percent styrene was suppliedand grafted continuously parts ofstyrene over a 1-hour period.Thereafter, 30 parts of methyl methacrylate was added and graftedcontinuously over a 1-hour period to provide a graft polymer. From 10parts of the graft polymer thus prepared and 90 parts of a copolymerconsisting of 93 percent vinyl chloride and 7 percent vinyl acetate wasprepared the resin composition. The impact strength and the luminoustransmittance of the resin composition were 62.8 kg.-cm./mm. and 78.6percent respectively.

EXAMPLE 18 To 55 parts of the elastomer consisting of 65 percent 1,3-butadiene, 12 percent n-butyl acrylate and 23 percent styrene wasgrafted first 28 parts of styrene while supplying of the monomer inhaving dissolved therein 2 parts of stearic acid continuously over al-hour period and thereafter 17 parts of methyl methacrylate was graftedto the product while supplying continuously the monomer in havingdissolved therein 1 part of stearic acid over a l-hour period to providea graft polymer. From 7 parts of the graft polymer and 93 parts of PVC(P 700) a resin composition was prepared. The impact strength and theluminous transmittance of the composition were 58.6 kg.-cm./mm. and 810percent respectively.

What is claimed is:

l. A resin composition comprising I. 3-40 parts by weight of a graftpolymer prepared by polymerizing first -50 percent by weight styrene inthe presence of 30-70 parts by weight of elastomer (E) prepared bycopolymerizing a monomer mixture comprising 75-30 percent by weight1,3-butadiene, 5-30 percent by weight n-butyl acrylate, and 20-50percent by weight styrene and having the component ratio within area(ABCD) in the ternary constitutional diagram of the accompanying drawingand then polymerizing 10-50 percent by weight methyl methacrylate, thetotal amount of said monomers being 70-30 parts by weight, and

II. 97-60 parts by weight of polyvinyl chloride or 97-60 parts by weightof a copolymer comprising more than 70 percent by weight vinyl chlorideand less than 30 percent by weight at least one of vinyl bromide, vinylacetate, vinylidene chloride, acrylic acid and methacrylic acid.

2. The resin composition as claimed in claim 1 wherein said graftpolymer is prepared by polymerizing styrene and methyl methacrylatewhile adding continuously at least one of the monomers to said elastomerover an at least 30-minute period.

3. The resin composition as claimed in claim 2 wherein at least one ofstyrene and methyl methacrylate to be polymerized in the presence ofsaid elastomer (E) has uniformly dissolved therein 0.5-5 percent byweight based on said graft polymer of a saturated fatty acid having10-18 carbon atoms.

4. The resin composition as claimed in claim 1 wherein said elastomer(E) is a terpolymer comprising 55-60 percent by weight 1,3-butadiene,8-13 percent by weight n-butyl acrylate, and 30-38 percent by weightstyrene.

2. The resin composition as claimed in claim 1 wherein said graftpolymer is prepared by polymerizing styrene and methyl methacrylatewhile adding continuously at least one of the monomers to said elastomerover an at least 30-minute period.
 3. The resin composition as claimedin claim 2 wherein at least one of styrene and methyl methacrylate to bepolymerized in the presence of said elastomer (E) has uniformlydissolved therein 0.5-5 percent by weight based on said graft polymer ofa saturated fatty acid having 10-18 carbon atoms.
 4. The resincomposition as claimed in claIm 1 wherein said elastomer (E) is aterpolymer comprising 55-60 percent by weight 1,3-butadiene, 8-13percent by weight n-butyl acrylate, and 30-38 percent by weight styrene.